Electrical recording instrument.



PATENTED MAR. 24, 1908.

APPLICATION FILED SEPT. 29. 1902.

3 SHEETS-SHEBT l.

ECnesse lnvenbor:

Lewis? Robinson PATENTBD MAR. 24, 1908.

L. T. ROBINSON.

ELECTRICAL RECORDING INSTRUMENT.

APPLICATION FILED SEPT. 29, 1902.

3 SHEETS-SHEET 2.

iilllHlllllllHii" lnvenCor:

} Robinso'h' a snmzrs-snnm a.

lnvenii'orz Lewvs'T. Robinson,

b3 J lff g L. T. ROBINSON.

. APPLICATIQN rum) SEPT. 29, 1802.

ELECTRICAL RECORDING INSTRUMENT.

Wgb.

1n: Nam"; rn'nu cov, WAsIINGYON, n. c.

UNITED STATES PATENT OFFICE.

LEWIS T. ROBINSON, OF SCHENEGTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL RECORDING INSTRUIVIENT.

Specification of Letters Patent.

Patented March 24, 1908.

Application filed September 29, 1902. Serial No. 125,194.

specification.

This invention relates to electric recording instruments for presentinga continuous record of changes in electric energy, such as current,potential or power.

The object of the invention is to provide an instrument which is moreaccurate than those commonly used. This end is accomplished by improvingthe mounting of the moving system, by owering the frictional resistanceof the recording pen or stylus, by giving the instrumentsuflicienttorque to negativethe errors dueto friction, and by improving thedamping mechanism so that the movements of the stylus under rapidchanges may be rendered dead-beat.

- In carrying out the invention I provide a motor for driving therecording strip of paper at acontrollable speed, and for marking on thepaper side by side with the record of elec- I 1 trio measurements a timescale controlled by a clock.- The recording style is a pen of pecul- 30iar construction in which the ink is drawn through a capillary tube froman ink-pot or I .Well carried by the arm which carries the pen.

The relations of the ink-well, feed pipe and stylus is such that thevery slight siphonic tendency of the feedpipe is just about balanced bythe resistance to flow due to its capillary bore. The flow of ink is,therefore, due entirely to the cohesion between the ink in the pen andthe ink which wets the pa )er, and is always proportional to the lengtof the path that the pen traces. This is of course the ideal conditionand the only condition under which freedom from bleeding is assured. Bythe term siphon capillary feed I mean to distinguish my pen from otherswhich are not intended to and do not operate on this principle. The armitself involves features of improvement in being provided with means forcounterbalancing the weight and adjusting the pen in the best Workingrelation to the record strip. The pen-carrying arm is provided with amagnetic damper comprising a body of metal moving throughout the rangeof defiection of the measuring arm within a magnetic field of force thedamping value of which may be accurately gaged by adjustment of thereluctance of the circuit. This device comprises two tapered polesforming the gap limits within which the damper moves, axially adjustableso as to vary the area and distance apart, either or both, ofconfronting pole-surface at the limits of the gap or its axial positionwith respect to the disk.

The features of novelty of the invention will be more particularlydescribed hereinafter and will be definitely indicated in'the claimsappended to this specification.

In the accompanying drawings, which illustrate the invention, Figure 1is a side elevation, partly broken away, of an instrument embodying myimprovements; Fig. 2 is a top plan view; Fig. 3 is a side elevationshowing the complete instrument on a smaller scale than that illustratedin Figs. 1 and 2; Fig. 4 is a plan of Fig. 3; Fig. 5 is a. diagrammaticrepresentation of the controlling circuits; Fig. 6 is a sectional viewon a magnified scale of the pen or recording style; Fig. 7 is anenlarged view of the measuring coils showing the method of mounting themovable system Fig. 8 is a view at right angles to that indicated inFig. 7; Fig. 9 1s a top plan; and Fig. 10 is a detail of the magnetcores which form the damping field.

The instrument may be mounted Within a suitable casing, as indicated inthe drawings, the driving member which feeds the paper being of anyapproved type. Such an instrument is shown at 1 as a spring-impelledmotor provided with a long spring to give a continuous run for aconsiderable length of time. Any other type of motor, as for eX- ample,an electric motor or a clock movement, might be employed for thispurpose.

- The motor shown has a long spring barrel 2 for increase of drivingcapacity, and is provided with a governor 3 which, in combination with afriction disk 4, admits of easy regulation of speed. This motor per seis of a standard type, and involves no features of my improvements. Themotor through a train of gears communicates motion at a suitable speedto a drum 5 over which a strip of paper is fed, being unwound from areel 6 and wound up on a take-off reel 7. The paper 15 punched at theedge at distances to re ister with pins 8 fixed radially in the drum,being guided over a curved metal bench or table 9 provided with a fiatface over which the measuring arm sweeps. This measuring arm is made ofthin sheet metal, such as aluminium, and is ointed between the movingsystem and the stylus, as indicated by the hinge 10. The two members areconnected by a light helical spring 11 capable of nice and delicateadjustment by a tension screw 12. The outer member of the arm carries alight ink well 13 which connects by a capillary tube 14 having thinwalls with a recording stylus. The construction of this style isiwellshown in Fig. 6. The outer member of the measuring arm carries a lightperforated stylus 15 provided at its tip with a bore of about 3 milsdiameter and short in length, the opening in the body of the stylusbeing enlarged by a counterbore, as shown in the sectional view in Fig.6, in which counterbore is seated a tapering plug 16 provided with ahandle by which it may be withdrawn and inserted at will. The clearancebetween the pin and the walls of the counterbore is sufficient to justpermit of free ink feed through the tube 14 to the ti of the fine borein the stylus.

The a ility to withdraw the plug 16 permits the pen to be readilycleaned in case of gumming or obstruction to the circulation of the ink,and since the supply tube for the stylus rests loosely on the edge or ina notch in the edge of the ink well it may be removed from the ink welland from the measuring arm by loosening a lock nut which holds thestylus to the measuring arm. The cleaning of the supply tube isfacilitated by this construction. The supply tube or feed pipe is curvedso that its open end is near the bottom of the ink well, and inrecording the ink is drawn through this feed pipe and into the stylus,against the action of capillary attraction in the feed pipe by the fmolecular cohesion of the liquid and its adhesion to the film which wetsthe paper. The tension screw 12 may be adjusted according to theconditions of service of the instrument. In cases where considerablevibration is met with, as on trolley cars and the like, the screw isslackened until the pen rests on the paper thus preventing jumping ofthe stylus. In cases where no serious vibration is met with, the s ringis put under tension so as to just leave the stylus clear of the paper,permitting no contact between the two ex cept through the very shortcolumn or film of 1n r. Thus there is almost no mechanical resistance todeflection of the measuring arm. The latter is secured to the armature17 which carries one of the control coils 17 of the instrument. Thiscoil in the present type of instrument is shown as excited by a' localsource of constant potential, as for example a storage battery, andincludes in its circuit an adjustable resistance 18, connection beingmade with the armature coil through flexible conducting spirals 19-19(see Fig. 5). In this same circuit are included the coils 202O" of thedamping magnet provided with tapered poles, as indicated at 2121 in Fig.10 and mounted so that they may be adjusted angularly relatively to oneanother. Thus two confronting pole faces may be adjusted so as toprovide limitmg planes to the air gap coextensive with the area of thepole tips, or less than this extent of surface by shifting them at anangle to one another, as indicated in Fig. 10, or both may be shifted asa unit; or only one need be wedge-shaped, the other being of circularface. Thus the damping effect may be delicately and nicely graduated byshifting the poles to difiierent angles, the gap directly across fromface to face being the path of least reluctance and the flux through theother portions of the pole faces being forced to traverse a path ofhigher reluctance when the poles are shifted to angular relative planes.Within this damping field moves a metal arm 22 which is connected bythin bars of metal with the rest of the movable member. The wholemovable arm may be made from a single piece as far as the hinged joint,being struck from sheet metal. This type of mounting gives an excellentdead-beat ac tion, and is a marked feature of improvement.

Another feature of importance in my invention is the mode of suspensionof the armature shaft and the zero-seeking element. This is indicated inFigs. 7 and 8, where a stout helical spring 23 is secured at one end toa fixed post forming a rigid part of the frame of the instrument, and atthe other end to the armature shaft. The lower end of the shaft hangsfreely in a cylindrical bearing; an adjustable stop 23 being provided toprevent excessive vibration of the axis. A set-screw 24 or other meansof adjusting the zero of the measuring arm may be used. The spring actsboth as a support and furnishes the zero seeking torque.

In series relation to the circuit which in-- cludes the damping magnetand one of the coils of the instrument is an adjustable resistance 18 bywhich the instrument may be set for different capacities of current. Current may be led into the movable coil 17 through the insulated bindingpost 25. The armature is provided with an iron core 26 laminatedtransverse to its axis which increases the torque of the instrument andis found on trial not to give trouble from hysteresis. The field coils17 have air cores. lVith this construction, with a source of constantpotential, such for example as a storage battery connected in onecircuit of the measuring instrument, and the source Whose fluctuationsarc to be measured on the other, the measuring arm will take a positiondepending on the energy or energy component in the circuit to bemeasured and in being deflected will leave a colored trace due to theink on the paper as the latter is drawn forward under the action of themotor.

In order to gage the time at any given stage of the record, anelectro-magnet 27 is mounted on the' frame which carries the drum, itsarmature carrying a small ink pot 28 and a capillary pen 29. hen thearmature is energized by closure of the circuit through aclock-controlled circuit closer exterior to the device, any suitableform of which may be employed, the pen 29' is drawn across the paper fora short distance so as to leave a projection or trace in ink, and asthese projections occur every second or at any other desired interval,the time of any oint of the measured cury e is indicated.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,

1. An electrical recording instrument having stationary and movableelements, one excited by a source of constant potential and the other bythe current or energy to be measured, a damping magnet in circuit withthe constant source, a conductor carried by the movable element andcutting the field of the magnet, a flexible jointed recording arm alsosecured to the movable element, a recording pen having a siphoncapillary feed carried by the arm, and means for sup orting arecordingsurface in cooperative re ation to the pen.

2. An electrical recording instrument having a moving element suspendedby a spring and comprising an armature, a flexible jointed arm, and arecording en having a siphon ca illary feed carried by said arm, fieldcoils or'cooperation with said armature, and means for supporting arecording surface beneath the pen.

3. An electrical recording instrument having a moving element suspendedby a spring and comprising an armature, a flexible arm, and a recordingpen having a siphon ca illary feed carried by said arm, an adjustab estop for preventing excessive vibration of the moving element, fieldcoils for cooperation with said armature, and means for supporting arecording'surface beneath the pen.

4. In an electrical recording instrument, a recording arm having astylus secured thereto, an ink well for supplying said stylus, and atube with one end secured to said stylus and the other end bent to enterthe ink well, said tube and ink well being relatively movable to permitwithdrawal of the tube from the ink well.

5. In an electrical recording instrument, a

recording arm having a stylus, means for removably securing said stylusto said arm, an ink well carried by said arm, and a tube bent to passover the edge of the ink well to bring one end near the bottom of saidwell and having the other end secured to said stylus.

6. In an electric recording instrument, a controlling device comprisingan inner element having a core of good magnetic permeability and a coilthereon, and an outer element consisting of a coil having an air core,said elements being relatively movable, aflexible jointed recording armsecured to the movable element, a pen carried by the arm, and means forsupporting a recording surface in cooperative relation to the pen.

7. In an electric recording instrument, a controlling device comprisingan inner element having a core of good magnetic permeability laminatedin the direction of magnetic flux, and an outer element consisting of acoil having an air core, said elements being relatively movable, 'ajointed recording arm secured to the movable element, a stylus carriedby the arm, and means for supporting a recording surface out ,of contactwith the stylus except through a film of fluid.

8. In an electric recording instrument, a controlling device comprisingan inner element having a core of good magnetic permeability and a coilthereon, and an outer element consisting of a coil having an air core,said elements being relatively .movable, a flexible recording armsecured to the movable element, a pen carried by the arm, means forsupporting a recording surface in cooperative relation to the pen, and amagnetic damper comprising a conductor carried by the movable elementand magnets whose pole tips are oblong and angularly adjustable wherebythe field strength may be varied.

9. In an electrical recording instrument, a recording arm in two partshinged together one part being a prolongation of the otherand providedwith an adjustable spring which holds the outer part yieldingly.

10. In an electrical recording instrument, a recording arm in two partshinged together, one part being a prolongation of the other and providedwith an adjustable spring which holds the outer part yieldingly, and arecord ing pen having a siphon capillary-feed carried by the outer part.

11. In an electrical recording instrument, a recording pen having astylus, an ink well, and a capillary tube acting as a siphon to feed inkfrom the well to the stylus, said stylus having a counter bore ofrelatively large diameter between its tip and its connection with thetube, and a tapering rcmovable plug in the counterbore.

12. An electrical recording instrument having a moving element and adamper cooperating therewith, said damper comprising a conductorattached to the moving clement and cutting the field created by magnetshavrotation With relation to each other varies ing coaxial opposing polepieces of such shape the reluctance of the path between them. 10 thatthe strength of the magnetic field may In Witness whereof, I havehereunto set my be varied by relative axial rotation of the hand this26th day of September, 1902.

5 pole pieces. LEWIS T. ROBINSON.

13. In a damper for electrical recording in- Vitnesses: struments,magnets arranged coaxially and G. C. HOLLISTER,

having pole pieces of such shape that their HELEN ORFORD.

